1. Field of the Invention
This invention relates to an injection molding machine in which a first injection mold having a central gate and any of various second injection molds having an off-center gate for forming an asymmetrical sprue are adapted to be installed and which comprises a horizontal clamping unit, which is mounted on a machine pedestal, and an injecting unit, which is mounted on a cast iron carrier, which is slidably mounted on horizontal tracks, wherein said injecting unit is adapted to assume a first operating position, in which the injection axis is centrally disposed and in which the injecting unit is movable to the central gate of said first injection mold, said injecting unit is movable in a transfer plane, which extends through the central injection axis, from to any one additional operating positions, in which said injection axis is off center, by means of a screw drive, which is supported on the machine pedestal and engages the carrier for the injecting unit and is adapted to hold the injecting unit in each of said additional operating positions, in which said injecting unit is movable to the off-center gate of any of the second injection molds through an elongate opening, which extends in said transfer plane.
2. Description of the Prior Art
In an injection molding machine of that kind which is known from German Utility Model No. 1,852,612, the injection mold is movable from the first operating position for filling a center-gate mold to any of the additional operating positions for filling a linear mold having a non-symmetrical gate by a pivotal movement in the transfer plane. As a result, the less conventional linear mold-filling process, which is preferably used to make plastic parts having large surfaces with use of a lateral sprue, may be carried out in the same injection molding machine in case of need whereas a shifting or swiveling of the injecting unit for pouring into the parting line of the mold is not required.
In a comparable injection molding machine which is known from German Utility Model No. 1,860,806 and Swiss Patent Specification No. 381,420, a parallel displacement in a horizontal or vertical direction can be imparted to the carrier for the injecting unit by means of a hydraulic shifting cylinder or by means of a screw drive to move the injecting unit to various operating positions.
Finally, it is also known to measure a displacement and particularly to control the relative movement of subassemblies of a machine, such as an injection molding machine, by means of linear potentiometers (see U.S. Pat. No. 4,680,570; prospectus of Novo-Technik KG, Offterdinger GmbH & Co., Horbstrasse 12, D-7302 Ostfildern 1).